1. Field of the Invention
The present invention relates to a control system that assists a shifting operation of a transmission and a saddle-straddling type vehicle including the same.
2. Description of the Related Art
When operating a gearshift in a vehicle with a manual transmission, first, a driver usually disengages a clutch. Thus, power transmission from a crankshaft of an engine to a main shaft of the transmission is stopped, so that gears are easily disconnected. In this state, the driver performs a shifting operation and changes gear positions. Finally, the driver engages the clutch, so that the power is transmitted from the crankshaft to the main shaft. In this manner, the gearshift is completed.
When the gearshift is required to be operated quickly in a race or other high speed activities, the driver operates the gearshift without a clutch operation (hereinafter referred to as “clutchless shifting”) in some situations. In such situations, since the gearshift is operated while the power is being transmitted from the crankshaft to the main shaft, it is difficult to disconnect the gears.
Therefore, a system that adjusts an output of the engine such that the gears can be easily disconnected during the clutchless shifting has conventionally been developed (see JP 7-34916 A, for example).
For example, the output of the engine is adjusted when the shifting operation is performed by the driver in the transmission control system described in JP 7-34916 A. Thus, a torque of the engine applied to the gears of the transmission is reduced, so that the gears are easily disconnected.
Generally, the gears of the transmission provided in a vehicle such as a motorcycle, have a dog clutch mechanism. In such a transmission, it is not easy for a less skilled driver to quickly engage the gears. Therefore, an engagement failure of the gears may occur in the transmission to cause the gears to be maintained in a disconnected state in some cases when the driver operates the clutchless shifting.
Here, the gears can be easily disconnected according to the transmission control system described in JP 7-34916 A. However, the foregoing engagement failure of the gears cannot be sufficiently prevented. Therefore, when an accelerator operation is performed with the gears of the transmission being disconnected, the rotational speed of the engine may be changed.
In this case, a large difference arises between the rotational speed of the main shaft of the transmission and the rotational speed of the drive shaft, so that a shift shock may occur in the vehicle at the time of completion of the shifting operation. This negatively impacts a driving feeling of the vehicle.